In the field of graphic arts, a image formation system providing a high contrast photographic property is required to provide excellent reproduction of an image of continuous gradation or a linear image by dot image process.
To this end, a special developing solution referred to as a lith developer has heretofore been used. A lith developer contains only hydroquinone as a developing agent. In order to avoid inhibiting infectious development thereof, the developer contains a sulfite as a preservative in the form of an addition product with formaldehyde so that the concentration of free sulfite ions is extremely low. This renders the developer extremely subject to oxidation by air. Thus, a conventional lith developer has a big disadvantage that it can not be stored for more than 3 days.
The process for obtaining a high contrast photographic property by using a stable developing solution is accomplished by a process which comprises using a hydrazine derivative as described in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,211,857 and 4,243,739. This process can provide a high contrast and a high sensitivity. In this process, a high concentration of sulfite can be added to the developing solution. Therefore, the developing solution is much more table to air oxidation than the conventional lith developer.
However, this process using a hydrazine derivative is disadvantageous in that since the pH value of the developer is higher than that of the common lith developer, a silver halide photographic material is more subject to uneven development when processed by means of an automatic developing machine which is commonly used in the art.
The mechanism of generation of uneven development is unknown. If the pH value of a developing solution is lower than that of the common lith developer, it causes no unevenness in development. However, a light-sensitive material containing a hydrazine derivative is not rendered high contrast. Even if a high pH developer providing a high contrast is used, there occurs no uneven development when the developer is free of auxiliary developing agent and contains only hydroquinone. However, such a developer containing only hydroquinone is disadvantageous in that when a silver halide photographic material is continuously processed by means of an automatic developing machine, the concentration of halogen ions in the developer (mainly bromide ions) is increased, causing a reduction in photographic sensitivity. Thus, it has been desired to use a compound which provides a high contrast when a developer containing a high pH auxiliary developing agent is used and also causes no unevenness in development without changing sensitivity while maintaining stable photographic properties even when a silver halide photographic material is continuously processed by means of an automatic developing machine.